Air conditioning and energy recovery system and method of operation

ABSTRACT

A system ( 20 ) for conditioning air ( 30 ) includes conditioning circuits ( 26, 28 ). Each of the circuits ( 26, 28 ) includes a heat transfer coil ( 54, 60 ) residing in a supply section ( 22 ) of the system ( 20 ), and a heat transfer coil ( 56, 62 ) residing in a return section ( 24 ) of the system ( 20 ). A controller ( 50 ) in communication with the circuits ( 26, 28 ) determines one of a heating mode ( 78, 110 ) and a cooling mode ( 148, 150 ) for an interior space ( 34 ). The controller ( 50 ) selectively actuates the conditioning circuits ( 26, 28 ) to condition outside air ( 30 ) entering the supply section ( 22 ) to produce conditioned supply air ( 36 ) for provision into space ( 34 ) and to recover heating and cooling energy from return air ( 38 ) entering the return section ( 24 ) from the space ( 34 ) prior to its discharge from the system ( 20 ) as exhaust air ( 44 ).

RELATED INVENTION

The present invention claims priority under 35 U.S.C. §119(e) to: “Outside Air-Air Conditioning/Energy Recovery Unit,” U.S. Provisional Patent Application Ser. No. 60/967,562, filed 4 Sep. 2007, which is incorporated by reference herein.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of air conditioning systems. More specifically, the present invention relates to an air conditioning system that includes an energy recovery capability.

BACKGROUND OF THE INVENTION

It is known that dependence on the natural exchange of air between the indoors and outdoors through air infiltration and exfiltration may not be satisfactory for good indoor air quality and moisture control. Accordingly, mechanical ventilation systems have been developed that use fans to maintain a flow of fresh outdoor air into a building (outside air stream) while exhausting out an equal amount of stale indoor air (exhaust air stream).

Unfortunately, these ventilation systems place additional burdens on the heating, ventilating, and air conditioning systems of a building. In particular, costly conditioned air is exhausted (along with contaminants) as the exhaust air stream, while the outside air stream must be brought in and conditioned (cooled, heated, and/or dehumidified) in order to provide a healthy environment in the building. Furthermore, these ventilation systems result in the loss of heating or cooling energy in the exhaust air. The problem of losing heating or cooling energy through the air exhausted from a building or facility has had a major impact in the form of wasted energy and high costs for heating, ventilating, and cooling buildings, institutions, and facilities.

This problem is exacerbated in commercial facilities and institutions that require one hundred percent outside air at high ventilation rates. The heating and cooling energy needed to condition this air, as well as the fan energy needed to move it, can be prohibitively costly. Moreover, with the high percentage of outdoor air mandated for commercial and institutional buildings, controlling indoor humidity levels can become a challenge.

Strategies for recovering at least a portion of this wasted energy have concentrated on separate systems and methods for recovering the lost heating or cooling energy through cross flow exchangers, run-around loops, heat wheels, heat pipes, and so forth. Each of these strategies try to scavenge the maximum amount of heating or cooling energy from the exhaust air stream and return that energy to precondition supply air. These systems, typically referred to as energy recovery ventilators, have generally been implemented in the colder regions of the United States, Canada, Europe, and Scandinavia for many years.

In warm areas, there is not a significant energy dollar savings from using energy recovery ventilators since they are not as effective in the cooling season and they can be quite costly. That is, the cost of the additional electricity consumed by the system fans may exceed the energy savings from not having to condition the supply air in mild climates. Nevertheless, pollutants generated in a building, facilities, or institutions can accumulate and reduce the indoor air quality to unhealthful levels. In addition, regulations governing commercial facilities and institutions that require one hundred percent outside air at high ventilation rates still apply in these warm areas.

Accordingly what is needed is a system and method for ensuring a healthy indoor environment and positive moisture control for an interior space in a variety of climates. What is further needed is a system and method for energy recovery that enable a facility's heating and cooling system to be downsized through lost energy recovery.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the Figures, wherein like reference numbers refer to similar items throughout the Figures, and:

FIG. 1 shows a perspective view of an air conditioning and energy recovery system in accordance with an embodiment of the invention;

FIG. 2 shows a plan view of the system of FIG. 1;

FIG. 3 shows a block diagram of a first conditioning circuit of the system of FIG. 1 in a heating mode;

FIG. 4 shows a block diagram of a second conditioning circuit of the system of FIG. 1 in a heating mode;

FIG. 5 shows a block diagram of the first conditioning circuit in a cooling mode;

FIG. 6 shows a block diagram of the second conditioning circuit in a cooling mode;

FIG. 7 shows a block diagram of the second conditioning circuit with a third conditioning circuit in a dehumidification mode;

FIG. 8 shows a flowchart of a system control process in accordance with another embodiment of the invention;

FIG. 9 shows a flowchart of a heating mode subprocess in accordance with the system control process;

FIG. 10 shows a flowchart of a cooling mode subprocess in accordance with the system control process; and

FIG. 11 shows a flowchart of a dehumidification mode subprocess in accordance with the system control process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention entails an air conditioning and energy recovery system. Another embodiment of the invention entails a method of controlling the air conditioning and energy recovery system so as to provide effective energy recovery in both the heating and cooling seasons. In particular, the system and methodology enable the recovery of lost energy (btu's) through the condenser cycle by using refrigerant (e.g., Freon) as the medium of energy recovery instead of conventionally utilized water or air. The incorporation of an energy recovery capability with an air conditioning system enables downsizing of the system relative to prior art heating, ventilation, and air conditioning systems. This downsizing is accomplished through a reduction in peak heating and cooling requirements. Downsizing can result in a system that is half the weight of prior art systems for rooftop mounting. Furthermore, the system and associated methodology can be readily implemented in environments that require one hundred percent outside air at high ventilation rates. In addition, the system is operable over a wide range of air conditions, such as from one hundred and twenty-two degrees Fahrenheit to as low as negative ten degrees Fahrenheit.

Referring to FIGS. 1 and 2, FIG. 1 shows a perspective view of an air conditioning and energy recovery system 20 in accordance with an embodiment of the invention, and FIG. 2 shows a plan view of system 20. System 20 is a heat pump, or air-conditioning unit, which is capable of heating and cooling by refrigeration, transferring heat from one (often cooler) medium to another (often warmer) medium. Accordingly, system 20 can provide cooling during warm weather and heating during cool weather. In accordance with the invention, system 20 includes integral energy recovery capability in order to recover wasted energy, reduce equipment and operating costs, and downsize the equipment relative to prior art systems through a reduction in peak heating and cooling requirements. In addition, system 20 is efficacious for use with commercial facilities and institutions, such as laboratories, kitchens, convention centers, casinos, gyms, factories, hospitals, animal kennels, and the like, that have high outside air requirements and humidity control requirements.

System 20 generally includes a supply section 22, a return section 24, a first conditioning circuit 26, and a second conditioning circuit 28. In general, outside air 30 is received at an inlet 32 of supply section 22. Outside air 30 is conditioned within supply section 22, and provided to an interior space 34 through the appropriate ducting (not shown) as supply air 36. In addition, return air 38 from interior space 32 is received at an inlet 40 of return section 24. Return air 38 is conditioned in return section 24 to selectively recover heating energy or cooling energy (discussed below) prior to its discharge from an outlet 42 of return section 24 outside of interior space 32 as exhaust air 44.

System 20 is located in a housing 46, or cabinet, that may be mounted on top of, for example, the roof of a business establishment. Housing 46 may include doors 48 for access to the components of system 20. Access through doors 48 enables ready removal, replacement, and/or servicing of fans, motors, and other components of system 20. A controller 50 may be located in part or in its entirety internal to housing 46. Alternatively, controller 50 may be located remote from housing 46 for ready access by a user. Controller 50 may control the components of system 20 via a wired or wireless connection.

First conditioning circuit 26 includes a first compressor 52, a first coil 54 residing in supply section 22, and a second coil 56 residing in return section 24. Likewise, second conditioning circuit 28 includes a second compressor 58, a third coil 60 residing in supply section 22, and a fourth coil 62 residing in return section 24. A fifth coil 64 additionally resides in supply section 22. Fifth coil 64 is a component of a third conditioning circuit 66 in selective fluid communication with second conditioning circuit 28 (discussed below). Supply section 22 further includes a filter 68, a supply fan 70, and an optional furnace 72. Return section 24 further includes a filter 74 and a return fan 76.

When system 20 is activated, supply fan 70 draws outside air 30 into supply section 22 through filter 68, which may be a 30/30 filter for filtering contaminants from outside air 30. Outside air 30 passes through furnace 72 where air 30 may be at least partially warmed during periods of extreme cold. Outside air 30 passes over first coil 54 where it may be selectively heated or cooled in accordance with a particular heating or cooling mode control stage. Likewise, outside air 30 passes over third coil 60 where it may be selectively heated or cooled in accordance with a particular heating or cooling mode control stage. Outside air 30 then passes by fifth coil 64 of third conditioning circuit 66 where it may be heated to dry it out, i.e. dehumidify, outside air 30 prior to the provision of the conditioned supply air 36 to interior space 34.

Additionally, when system 20 is activated, return fan 76 draws return air 38 into return section 24 through filter 74, which may be a 30/30 filter for filtering contaminants from return air 38. Return air 38 passes over second coil 56 where the heating or cooling energy of return air 38 may be recovered in accordance with a particular heating or cooling mode control stage via a refrigerant loop. Return air 38 then passes over fourth coil 62 where additional heating or cooling energy of return air 38 may be recovered in accordance with a particular heating or cooling mode control stage prior to its discharge from outlet 42 as exhaust air 44.

The heating and cooling modes for first and second conditioning circuits 26 and 28 are discussed in connection with FIGS. 3-6. The dehumidification mode for third conditioning circuit 66 is discussed in connection with FIG. 7. In addition, a system control process and the various operational stages for each of the heating, cooling, and dehumidification modes are discussed in connection with FIGS. 8-11.

FIG. 3 shows a block diagram of first conditioning circuit 26, also referred to as circuit A, of system 20 (FIG. 1) in a heating mode 78. First conditioning circuit 26 includes compressor 52, first coil 54, and second coil 56 in fluid communication via a fluid loop 80. In one embodiment, compressor 52 may carry a larger load than compressor 58 (FIG. 2) of second conditioning circuit 28. For example, compressor 52 may be a thirteen ton compressor, whereas compressor 58 may be a nine ton compressor. A direction of fluid (i.e., refrigerant) through fluid loop 80 is governed by a reversing valve 82 positioned in fluid loop 80 having an input 84 in fluid communication with an outlet 86 of compressor 52. Per convention, a receiver 88 may be positioned in fluid loop 80 having an outlet 90 in fluid communication with an inlet 92 of compressor 52.

A metering device 94, which may be in the form of a restrictor or an expansion valve, and a bypass line 96 are located in fluid loop 80 and are associated with first coil 54. Selection of a fluid route through metering device 94 or bypass line 96 is accomplished by actuation of a bypass valve 98. A fluid filter 100 may be in fluid communication with metering device 94. Likewise, a metering device 102 and a bypass line 104 are located in fluid loop 80 and are associated with second coil 56. Selection of a fluid route through metering device 102 or bypass line 104 is accomplished by actuation of a bypass valve 106.

In heating mode 78, reversing valve 82 is energized to enable a flow of refrigerant from compressor 52 toward first coil 54 via fluid loop 80. That is, relatively high pressure refrigerant, denoted by arrows 108, is discharged in a gaseous form from compressor 52 via fluid loop 80 to first coil 54. As cool outside air 30 passes through first coil 54, outside air 30 removes heat from (i.e., cools) refrigerant 108 so that outside air 30 is warmed. The warmed outside air 30 subsequently passes through additional components of supply section 22 (discussed above) and is delivered as warm supply air 36 to space 34. The cooled refrigerant 108 continues through fluid loop 80 via bypass line 96 and passes through metering device 102.

Metering device 102 controls the pressure and flow of refrigerant 108 into second coil 56, residing in return section 24. As the warmed return air 38 passes through return section 24, the cooled refrigerant 108 in second coil 56 removes heat from (i.e., cools) return air 38 so that exhaust air 44 is cooled. Relatively low pressure refrigerant 108 returns to compressor 52 from second coil 56 via fluid loop 80 and receiver 88 where the refrigeration cycle is continued. Thus, refrigerant 108 is at least partially warmed by the heat energy in return air 38 that would normally have been wasted. This recovered heat energy enables the high pressure refrigerant 108 entering first coil 54 to be warm relative to outside air 30 so as to warm outside air 30.

FIG. 4 shows a block diagram of second conditioning circuit 28, also referred to as Circuit B, of system 20 (FIG. 1) in a heating mode 110. Second conditioning circuit 28 includes second compressor 58, third coil 60, and fourth coil 62 in fluid communication via a fluid loop 112. A direction of fluid (i.e., refrigerant) through fluid loop 112 is governed by a reversing valve 114 positioned in fluid loop having an input 116 in fluid communication with an outlet of second compressor 58. A receiver 120 may be positioned in fluid loop 112 having an outlet 122 in fluid communication with an inlet 124 of compressor 58.

A metering device 126, which may be in the form of a restrictor or an expansion valve, and a bypass line 128 are located in fluid loop 112 and are associated with third coil 60. Selection of a fluid route through metering device or bypass line 128 is accomplished by actuation of a bypass valve 130. A fluid filter 132 may be in fluid communication with metering device 126. Likewise, a metering device 134 and a bypass line 136 are located in fluid loop 112 and are associated with fourth coil 62. Selection of a fluid route through metering device 134 or bypass line 136 is accomplished by actuation of a bypass valve 138.

In heating mode 110, reversing valve 114 is energized to enable a flow of refrigerant from compressor 58 toward third coil 60 via fluid loop 112. That is, relatively high pressure refrigerant, denoted by arrows 140, is discharged in a gaseous form from compressor 58 via fluid loop 112 to third coil 60. As cooler outside air 30 passes through coil 60, outside air 30 removes heat from (i.e., cools) refrigerant so that outside air 30 is warmed. The warmed outside air 30 subsequently passes through additional components of supply section 22 (discussed above) and is delivered as warm supply air 36 to space 34. The cooled refrigerant 140 continues through fluid loop 112 via bypass line 128 and passes through metering device 134.

Metering device 134 controls the pressure and flow of refrigerant 140 into fourth coil 62, residing in return section 24 (FIG. 2). As the warmed return air 38 passes through return section 24, the cooled refrigerant 140 in fourth coil 62 removes heat from (i.e., cools) return air 38 so that exhaust air 44 is cooled. Relatively low pressure refrigerant 140 returns to compressor 58 from fourth coil 62 via fluid loop 112 and receiver 120 where the refrigeration cycle is continued. Thus, refrigerant 140 is at least partially warmed by the heat energy in return air 38 that would normally have been wasted. This recovered heat energy enables the high pressure refrigerant 140 entering second coil 60 to be warm relative to outside air 30 so as to warm outside air 30. The activation of first conditioning circuit 26 (FIG. 3) in heating mode 78 (FIG. 3) and/or second conditioning circuit 28 in heating mode 110 will be discussed in connection with FIG. 9.

Third conditioning circuit 66 is also in communication with second conditioning circuit 28 via a fluid loop 142. Third conditioning circuit 66 includes a reheat valve 144, a compressor 146, and fifth coil 64 in fluid communication via fluid loop 142. Reheat valve 144 may be selectively enabled to allow a flow of fluid though fluid loop 142 into compressor 146 and fifth coil 64 and return that fluid to fluid loop 112 of second conditioning circuit 28 when the dehumidification of outside air 30 is required. A dehumidification mode is discussed in connection with FIGS. 7 and 11 and is typically executed in connection with a cooling mode for either of first and second conditioning circuits 22 and 24.

FIG. 5 shows a block diagram of first conditioning circuit 26 in a cooling mode 148. In cooling mode 148, reversing valve 82 is disabled to enable a default flow of refrigerant 108 from compressor 52 away from first coil 54 and toward second coil 56 via fluid loop 80. That is, relatively high pressure refrigerant 108 is discharged in a gaseous form from compressor 52 via fluid loop 80 to second coil 56.

At second coil 54, refrigerant 108 is condensed and cooled by the action of the cooler return air 34, flowing through second coil 44. That is, refrigerant 108 absorbs the cooling energy from return air 34 otherwise wasted in exhaust air 44. Refrigerant 108 flows via bypass line 104 and fluid loop 80 to metering device 94. Metering device 94 controls the pressure and flow of refrigerant 108 into first coil 54. As warm outside air 30 passes through first coil 54, refrigerant 108 in first coil 54 removes heat (i.e., cools) outside air 30. The cooled outside air 30 subsequently passes through additional components of supply section 22 (discussed above) and is delivered as cool supply air 36 to space 34. Warmed refrigerant 108 exits first coil 54 and is returned via fluid loop 80 to compressor 52 where the refrigeration cycle is continued.

FIG. 6 shows a block diagram of second conditioning circuit 28 in a cooling mode 150. In cooling mode 150, reversing valve 114 is disabled to enable a default flow of refrigerant 140 from compressor 58 away from third coil 60 and toward fourth coil 62 via fluid loop 112. That is, relatively high pressure refrigerant 140 is discharged in a gaseous form from compressor 58 via fluid loop 112 to fourth coil 62.

At fourth coil 62, refrigerant 140 is condensed and cooled by the action of the cooler return air 38, flowing through fourth coil 62. That is, refrigerant 140 absorbs the cooling energy from return air 34 otherwise wasted in exhaust air 44. Refrigerant 140 flows via bypass line 136 and fluid loop 112 to metering device 126. Metering device 126 controls the pressure and flow of refrigerant 140 into third coil 60. As warm outside air 30 passes through third coil 60, refrigerant 140 in third coil 60 removes heat (i.e., cools) outside air 30. The cooled outside air 30 subsequently passes through additional components of supply section 22 (discussed above) and is delivered as cool supply air 36 to space 34. Warmed refrigerant 140 exits third coil 60 and is returned via fluid loop 112 to compressor 58 where the refrigeration cycle is continued. The activation of first conditioning circuit 26 (FIG. 5) in cooling mode 148 (FIG. 5) and/or second conditioning circuit 28 in cool mode 150 will be discussed in connection with FIG. 10.

FIG. 7 shows a block diagram of second conditioning circuit 28 with third conditioning circuit 66 in a dehumidification mode 152. Under certain conditions, and particularly during the hot season, the moisture content of outside air 30 may be undesirably high. That is, outside air 30 is humid, or saturated with moisture. Accordingly, it may be desirable to dehumidify supply air 36 prior to its provision to interior space 34.

When outside air 30 is to be dehumidified in connection with either of cooling modes 148 and 150, reheat valve 144 is enabled to allow a flow of warm, high pressure refrigerant 140 into fluid loop 142. Refrigerant passes through compressor 146 and into fifth coil 64 residing in supply section 22 (FIG. 2). Outside air 30 passing through fifth coil 64 is heated by a few degrees, for example, eight degrees, to dry (i.e., dehumidify) outside air prior to its provision into space 34 and supply air 36. Cooled refrigerant 140 exiting fifth coil 64 is returned via fluid loop 142 to fluid loop 112.

FIG. 8 shows a flowchart of a system control process 154 in accordance with another embodiment of the invention. System control process 154 may be executed by controller 50 (FIG. 2) to determine whether air conditioning and energy recovery system should operate in a heating mode or a cooling mode with or without a dehumidification mode.

System control process begins with a task 156. At task 156, temperature and humidity of interior space 34 (FIG. 2) is detected. Next, at a task 158, temperature and humidity of outside air 30 is detected.

In response to tasks 156 and 158, controller 50 determines whether system 20 should be placed in a heating mode, for example, when the temperature (either sensible or wet bulb) of outside air 30 (FIG. 1) drops below a predetermined heating threshold. When a determination is made that system 20 should go into a heating mode, control process 154 proceeds to a task 162. At task 162, system 20 enters a heating mode subprocess, discussed in connection with FIG. 9. However, when a determination is made that system 20 should not be placed in a heating mode, control process 154 proceeds to a query task 164.

At query task 164, controller 50 determines whether system 20 should be placed in a cooling mode, for example, when outside temperature (either sensible or wet bulb) rises above a predetermined cooling threshold. When a determination is made that system 20 should go into a cooling mode, control process 154 proceeds to a task 166. At task 166, system 20 enters a cooling mode subprocess, discussed in connection with FIG. 10. At task 166, a determination may additionally made as whether to perform a dehumidification mode subprocess in conjunction with the cooling mode subprocess. This determination may be made when, for example, the humidity of outside air 30 (FIG. 1) exceeds a predetermined humidity threshold. When outside air 30 is to be dehumidified, a dehumidification mode subprocess, discussed in connection with FIG. 11, will be performed in conjunction with the cooling mode subprocess.

At query task 164, when a determination is made that system 20 should not be placed in a cooling mode, control process 154 proceeds to a task 168. At task 168, the temperature and humidity of outside air 30 are such that it does not require heating, cooling, or dehumidification. As such, system 20 can go into a free cooling state with just ventilation being provided through the activation of supply fan 70 (FIG. 2) and return fan 76 (FIG. 2).

Following any of tasks 162, 166, and 168, process control loops back to task 156 to continue monitoring indoor and outdoor temperatures and to control heating, cooling, and dehumidification as required.

FIG. 9 shows a flowchart of a heating mode subprocess 170 in accordance with system control process 154 (FIG. 8). Heating mode subprocess 170 is performed when a determination is made at query task 160 that system 20 is to enter a heating mode.

Heating mode subprocess 170 begins with a task 172. At task 172, controller 50 (FIG. 2) determines an appropriate heating stage to perform. Controller 50 may be a proportional-integral-derivative (PID) controller. A PID controller is a control loop feedback mechanism typically used in industrial control systems. A PID controller attempts to correct the error between a measured process variable (e.g., measured indoor air temperature and humidity) and a desired setpoint (e.g., desired indoor air temperature and humidity) by calculating and then outputting a corrective action that can adjust the heating and/or cooling accordingly.

A task 174 is performed in cooperation with task 172. At task 176, controller 50 selects and initiates execution of a heating mode stage.

In an exemplary configuration, controller 50 selects a desired heating mode stage from one of four operational stages—Stage 1: low heat requirement 176, Stage 2: moderate heat requirement 178, Stage 3: moderate-to-high heat requirement 180, and Stage 4: high heat requirement 182. In this example, each progressively higher numerical “stage” represents conditions in which the temperature of outdoor air 30 is progressively lower (i.e., colder), thus requiring progressively greater work from first and/or second conditioning circuits 26 and 28 to achieve and maintain a desired set point in interior space 34 (FIG. 1).

Following the initiation of any of stages 176, 178, 180, and 182, at task 174 the desired “stage” of heating will continue in response to the temperature of space 34, as well as the temperature of outdoor air 30. When heating is no longer required, heating mode subprocess 170 exits. Each of stages 176, 178, 180, and 182 is discussed briefly below.

At Stage 1: low heat requirement 176, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is de-energized, reheat valve 144 (FIG. 4) is disabled, and furnace 72 (FIG. 2) is off. In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B 28 is energized. Thus, execution of Stage 1: low heat requirement 176 results in only heating mode 110 (FIG. 4).

At Stage 2: moderate heat requirement 178, supply and return fans 70 and 76, respectively, are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In addition, first conditioning circuit, circuit B, 28 (FIG. 4) is de-energized, reheat valve 144 (FIG. 4) is disabled, and furnace 72 is off. Now, however, first conditioning circuit, circuit A, 26 is energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 26 is energized. Consequently, execution of Stage 2: moderate heat requirement 178 results in only heating mode 78 (FIG. 3).

At Stage 3: moderate-to-high heat requirement 180, supply and return fans 70 and 76, respectively, are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 26 is energized. In addition, second conditioning circuit, circuit B, 28 is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B is energized. However, reheat valve 144 (FIG. 4) is disabled and furnace 72 (FIG. 2) is off. Consequently, execution of Stage 3: moderate-to-high heat requirement 180 results in both heating mode 78 (FIG. 3) and heating mode 110 (FIG. 4).

At Stage 4: high heat requirement 182, supply and return fans 70 and 76, respectively, are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 26 is energized. In addition, second conditioning circuit, circuit B, 28 is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B is energized. Reheat valve 144 (FIG. 4) is disabled, but in this instance, furnace 72 is enabled. Consequently, execution of Stage 4: high heat requirement 182 results in both heating mode 78 (FIG. 3) and heating mode 110 (FIG. 4), as well as supplemenal heating from furnace 72.

FIG. 10 shows a flowchart of a cooling mode subprocess 184 in accordance with system control process 154 (FIG. 8). Cooling mode subprocess 184 is performed when a determination is made at query task 164 (FIG. 8) that system 20 is to enter a cooling mode.

Cooling mode subprocess 184 begins with a task 186. At task 186, controller 50 (FIG. 2) determines an appropriate cooling mode stage to perform, as discussed in connection with task 172 (FIG. 9) of heating mode subprocess 170 (FIG. 9). A task 188 is performed in cooperation with task 186. At task 188, controller 50 selects and initiates execution of a cooling mode stage.

In an exemplary configuration, controller 50 selects a desired cooling mode stage from one of six operational stages—Stage 1: low cool/dehumidification requirement 190, Stage 2: low cool no dehumidification requirement 192, Stage 3: moderate cool no dehumidification requirement 194, Stage 4: moderate-to-high cool no dehumidification requirement 196, Stage 5: high cool/dehumidification requirement 198, and Stage 6: high cool no dehumidification requirement 200. In this example, each progressively higher numerical “stage” represents conditions in which the temperature of outdoor air 30 is progressively higher (i.e., colder) and/or more humid, thus requiring progressively greater work from first and/or second conditioning circuits 26 and 28 to achieve and maintain a desired set point in interior space 34 (FIG. 1).

Following the initiation of any of stages 190, 192, 194, 196, 198, and 200, at task 188 the desired “stage” of cooling will continue in response to the temperature of space 34, as well as the temperature of outdoor air 30. When cooling is no longer required, cooling mode subprocess 184 exits. Each of stages 190, 192, 194, 196, 198, and 200 is discussed briefly below. Although not expressly stated below, it should be understood that since the following stages 190, 192, 194, 196, 198, and 200 are related to cooling, furnace 72 (FIG. 2) will always be off.

At Stage 1: low cool/dehumidification requirement 190, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is de-energized. In this instance, reheat valve 144 (FIG. 4) is enabled and modulated by a dehumidification subprocess 202 (FIG. 11). In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B 28 is disabled. Thus, execution of Stage 1: low cool/dehumidification requirement 190 results in cooling mode 150 (FIG. 6) with an accompanying dehumidification mode 152 (FIG. 7).

At Stage 2: low cool no dehumidification requirement 192, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is de-energized. Since dehumidification is not required, reheat valve 144 (FIG. 4) is disabled. In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B 28 is disabled. Thus, execution of Stage 2: low cool no dehumidification requirement 192 results in only cooling mode 150 (FIG. 6).

At Stage 3: moderate cool no dehumidification requirement 194, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is de-energized and reheat valve 144 (FIG. 4) is disabled. However, first conditioning circuit, circuit A, 26 (FIG. 3) is energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 26 is disabled. Thus, execution of Stage 3: moderate cool no dehumidification requirement 194 results in only cooling mode 148 (FIG. 5).

At Stage 4: moderate-to-high cool no dehumidification requirement 196, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is de-energized and reheat valve 144 (FIG. 4) is disabled. However, first conditioning circuit, circuit A, 26 (FIG. 3) is energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 26 is disabled. Thus, execution of Stage 3: moderate cool no dehumidification requirement 196 results in only cooling mode 148 (FIG. 5), but at a greater supply fan 70 speed then that of Stage 3 194.

At Stage 5: high cool/dehumidification requirement 198, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In this instance, reheat valve 144 (FIG. 4) is enabled and modulated by dehumidification subprocess 202 (FIG. 11). In addition, both first conditioning circuit, circuit A, 26 (FIG. 3) and second conditioning circuit, circuit B, 28 (FIG. 4) are energized and their corresponding reversing valves 82 and 114 are disabled. Thus, execution of Stage 5: high cool/dehumidification requirement 198 results in both cooling mode 148 (FIG. 5) and cooling mode 150 (FIG. 6), as well as dehumidification mode 152 (FIG. 7).

At Stage 6: high cool no dehumidification requirement 200, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In this instance, reheat valve 144 (FIG. 4) disabled. In addition, both first conditioning circuit, circuit A, 26 (FIG. 3) and second conditioning circuit, circuit B, 28 (FIG. 4) are energized and their corresponding reversing valves 82 and 114 are disabled. Thus, execution of Stage 5: high cool no dehumidification requirement 200 results in both cooling mode 148 (FIG. 5) and cooling mode 150 (FIG. 6).

FIG. 11 shows a flowchart of a dehumidification mode subprocess 202 in accordance with system control process 154 (FIG. 8).

Dehumidification mode subprocess 202 begins with a task 204. At task 204, controller 50 (FIG. 2) determines an appropriate dehumidification mode stage to perform. A task 206 is performed in cooperation with task 204. At task 206, controller 50 selects and initiates execution of a dehumidification mode stage.

In an exemplary configuration, controller 50 selects a desired dehumidification mode stage from one of three operational stages—Stage 1: first dehumidification requirement 208, Stage 2: second dehumidification requirement 210, and Stage 3: third dehumidification requirement 212. Following the initiation of any of stages 208, 210, and 212, at task 206 the desired “stage” of dehumidification will continue in response to the humidity of space 34, as well as the humidity of outdoor air 30. When dehumidification is no longer required, dehumidification mode subprocess 202 exits. Each of stages 208, 210, and 212 is discussed briefly below.

Stage 1: dehumidification requirement 208, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 5300 cubic-feet-per-minute (cfm) and return fan 76 may be set to 6000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) is de-energized. In this instance, reheat valve 144 (FIG. 4) is enabled and modulated. In addition, second conditioning circuit, circuit B, 28 (FIG. 4) is energized and reversing valve 114 (FIG. 4) for second conditioning circuit B 28 is disabled. Thus, execution of Stage 1: dehumidification requirement 208 results in dehumidification mode 152 (FIG. 7).

Stage 2: dehumidification requirement 210, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In addition, first conditioning circuit, circuit A, 26 (FIG. 3) de-energized and reversing valve 82 (FIG. 3) for first conditioning circuit A 22 is disabled. In this instance, reheat valve 144 (FIG. 4) disabled and second conditioning circuit, circuit B, 28 (FIG. 4) is de-energized. Thus, execution of Stage 2: dehumidification requirement 210 results in no dehumidification occurring, which may be the operational mode when only ventilation is called for at task 168 (FIG. 8) of system control process 154 (FIG. 8).

At Stage 3: dehumidification requirement 212, supply and return fans 70 and 76, respectively, (FIG. 2) are set to a desired fan speed. For example, supply fan 70 may be set to 4200 cubic-feet-per-minute (cfm) and return fan 76 may be set to 5000 cfm. In this instance, reheat valve 144 (FIG. 4) is enabled and modulated. In addition, both first conditioning circuit, circuit A, 26 (FIG. 3) and second conditioning circuit, circuit B, 28 (FIG. 4) are energized and their corresponding reversing valves 82 and 114 are disabled. Thus, execution of Stage 3: dehumidification requirement 198 results in dehumidification mode 152 (FIG. 7).

In summary, the present invention teaches an air conditioning and energy recovery system and a method of controlling the air conditioning and energy recovery system so as to provide effective energy recovery in both the heating and cooling seasons over a full range of temperature (e.g., from one hundred and twenty-two degrees Fahrenheit down to negative ten degrees Fahrenheit). The energy recovery capability is integral to the air conditioning system to enable downsizing of the system relative to prior art heating, ventilation, and air conditioning systems. This downsizing is accomplished through a reduction in peak heating and cooling requirements. Furthermore, the system and associated methodology can be readily implemented in environments that require one hundred percent outside air at high ventilation rates.

Although the preferred embodiments of the invention have been illustrated and described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims. For example, the system can be adapted to include more or less stages of heating mode, cooling mode, and dehumidification mode then that which was described. In addition, various mathematical and intuitive techniques can be used for determining which stage of cooling, heating, and/or dehumidification may be implemented in response to temperature and humidity requirements. 

1. A system for conditioning air entering an interior space comprising: a first conditioning circuit for carrying a first fluid, said first conditioning circuit including a first coil, a second coil, and a first compressor interposed between said first and second coils, said first coil, said second coil, and said first compressor being in communication via a first fluid loop; a second conditioning circuit for carrying a second fluid, said second conditioning circuit including a third coil, a fourth coil, and a second compressor interposed between said first and second coils, said third coil, said fourth coil, and said second compressor being in communication via a second fluid loop; a supply section having an inlet for receiving outside air and having an outlet for providing supply air to said interior space, said first and third coils residing in said supply air section; a return section having an inlet for receiving return air from said interior space and for releasing said return air as exhaust air outside of said interior space, said second and fourth coil residing in said return section; and a controller in communication with said first and second conditioning circuits, wherein said controller determines one of a heating mode and a cooling mode for said interior space and selectively actuates said first and second conditioning circuits in response to said one of said heating mode and said cooling mode.
 2. A system as claimed in claim 1 further comprising a third conditioning circuit, said third conditioning circuit comprising a fifth coil, a third compressor, and a third fluid loop, said fifth coil residing in said supply section, and said third fluid loop being in communication with said second fluid loop of said second conditioning circuit, wherein said controller determines a dehumidification mode and selectively actuates said third conditioning circuit in response to said dehumidification mode.
 3. A method of conditioning air entering an interior space comprising: conveying outside air through a first heat transfer coil residing in a supply section of a conditioning system; selectively transferring heat energy between said outside air and said first heat transfer coil; conveying said outside air through a second heat transfer coil residing in said supply section; selectively transferring said heat energy between said outside air and said second heat transfer coil; delivering said outside air as conditioned supply air to an interior space; receiving return air from said interior space to a return section of said conditioning system; conveying said return air through a third heat transfer coil residing in said return section; selectively exchanging said heat energy between said return air and said third heat transfer coil; conveying said return air through a fourth heat transfer coil residing in said return section; selectively exchanging said heat energy between said return air and said fourth heat transfer coil; and exhausting said return air as exhaust air outside of said interior space. 